Gregory Stark wrote: > "Bruce Momjian" <[EMAIL PROTECTED]> writes: > > > I have added another idea for index-only scans to the TODO list: > > > >> A third idea would be for a heap scan to check if all rows are visible > >> and if so set a per-table flag which can be checked by index scans. > >> Any change to the table would have to clear the flag. To detect > >> changes during the heap scan a counter could be set at the start and > >> checked at the end --- if it is the same, the table has not been > >> modified --- any table change would increment the counter. > > I think I would prefer to address this in the same infrastructure as the > dead-space-map. That way you're not dependent on having no updates happening > on the table at all. Any tuples on pages which contain no in-doubt tuples > could have their visibility check skipped but when you come across a tuple on > a page which has been modified since the last vacuum then you have to check > the visibility.
Yea, the bitmap/page idea is already on the TODO list. This was just a less granular idea. -- Bruce Momjian <[EMAIL PROTECTED]> http://momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
